Wideband Decoupled Asynchronously Coupled Patch Antennas

This article proposes a novel single-layer wideband decoupling method for patch antennas, eliminating the need for bulky decoupling structures. The approach involves two portions: multiple modes generation and modes superposition. First, asynchronously coupled patch (ACP) resonators are used to generate two pairs of copolarized odd and even modes, aided by characteristic mode (CM) analysis. Next, A lossy four-coupled resonator circuit is proposed to characterize these ACP resonators, with a mode-multiplexed central load guiding the decoupling process. The process reallocates the eigenfrequencies of two even modes while fixing odd modes. Building upon this, the input conductance of both odd and even modes is adjusted to align with the port conductance, ensuring wideband decoupling under optimal impedance matching. The proposed decoupling method is validated through the design and experimental testing of two antenna pairs and a 1-by-4 array. Antenna pairs demonstrate over 25 dB port isolation across bands of 3.44–4.57 GHz (28.2%) and 3.58–4.71 GHz (27.3%). Multipath coupling suppression involving adjacent and nonadjacent elements is investigated in an array configuration with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.42~\lambda _{0}$ </tex-math></inline-formula> element spacing, with exceeding 22 dB isolation across the band of 3.52–4.58 GHz (26.2%). This decoupling technique provides a cost-effective and fabrication-friendly solution for wideband multiple-input-multiple-output (MIMO) and phased array antennas.